Method for Producing a Can and Can Produced by Said Method

ABSTRACT

The method is provided for producing a can, including a jacket-shaped can body, which has at least one opening that is tightly closed by a peelable sealing membrane. The sealing membrane is provided with a pull tab, which is folded over and detachably connected to an upper side of the sealing membrane. The pull tab is detachably fastened to the upper side of the sealing membrane by way of an adhesive. The adhesive is printed onto the upper side of the sealing membrane and/or onto the pull tab. The adhesive is preferably a paint and in particular a sealing wax.

The invention relates to a method for producing a can comprising a jacket-shaped can body which has at least one opening that is tightly closed by a peelable sealing membrane and which is provided with a pull tab which is folded over and detachably connected to an upper side of the sealing membrane.

The invention additionally relates to a can which has been produced by this method.

In the prior art, such methods and cans have been known for a long time. For instance, CH 475 136 discloses a can having a sealing membrane which is fixed tightly to a retaining ring. The retaining ring has an annular inner part serving as a support for the sealing membrane. The sealing membrane is produced from an aluminum foil or paper-laminated aluminum foil. The sealing membrane is bonded fixedly to the retaining ring by adhesive bonding or hot-sealing. A pull tab serves to grip and pull the sealing membrane off the retaining ring.

A further can has been disclosed in the prior art by EP-A-1 541 494. Here, too, the can is sealed by a peelable sealing membrane. The peelable sealing membrane has a one-piece tab for opening the can.

Such cans have placed upon them the requirement that the pull tab is folded onto the surface of the lid. If the sealing membrane has a high proportion of aluminum, then the pull tab can be folded over in such a way that it lies flat on the lid. Since, in the case of a sealing membrane, the restoring force is low because of the high proportion of aluminum, the pull tab does not have to be fixed. It thus remains in the folded state without any fixing.

Increasingly, sealing membranes are required which have no aluminum or a comparatively low proportion thereof. Such sealing membranes can be produced from composite films having a high proportion of plastic and/or paper. However, it is disadvantageous here that the folded pull tab has to be fixed, since the sealing membrane has a high restoring force. Hitherto, hot-melt has been used as an adhesive for fixing the pull tab. The adhesive is applied in point form to the sealing membrane or to the pull tab. However, it is disadvantageous that hot-melt can be obtained in sterilizable form but is difficult to apply. In particular, closed systems are necessary.

The invention is based on the object of devising a method of the aforementioned type which permits sterilization of the can but nevertheless can be carried out inexpensively.

In a method of the generic type, the object is achieved in accordance with claim 1. In the method according to the invention, an adhesive that withstands sterilization is applied during the printing operation. This adhesive can be applied, for example, by flexo printing, digital printing or gravure printing. Such printing processes are suitable in particular for the application of a sealing wax, which withstands sterilization.

The application of the adhesive in the method according to the invention is a printing operation. This permits a particularly inexpensive method. Since, in the method according to the invention, a sealing membrane having a smaller proportion of aluminum or even no aluminium can be used, the proportion of waste can be reduced substantially. For instance, sealing membranes having a thickness of 0.05 mm can be used. The method according to the invention thus permits inexpensive production of cans which can be sterilized and which, in addition, can be opened simply with a pull tab.

According to a development of the invention, provision is made for the pull tab, after being folded over, to be connected to the upper side of the sealing membrane by welding. The welding and fixing of the pull tab can be carried out very simply and quickly, for example by means of ultrasound, a permanently heated bar or a sonotrode. This method step can be carried out very inexpensively in series with the lid production process.

According to a development of the invention, the sealing membrane is produced from a composite film. This has, for example, one or more layers of polyester, a comparatively thin layer of aluminum, the printed layer and a layer which connects the sealing membrane peelably to the retaining ring.

The can according to the invention is characterized in that the adhesive is arranged on the sealing membrane and/or the pull tab as part of an imprint and said adhesive connects the bent-over pull tab detachably to the upper side of the sealing membrane. The adhesive, as part of the imprint, can intrinsically have any desired form. For example, it can be formed in the shape of a point or the shape of a line. Here, this is preferably a sterilized can which is provided to hold a foodstuff.

Further advantageous features emerge from the dependent patent claims, the following description and the drawing.

Exemplary embodiments of the invention will be explained in more detail below by using the drawing, in which:

FIG. 1 shows a partial section through a can according to the invention,

FIG. 2 shows a plan view of part of the upper side of the sealing membrane,

FIG. 3 shows a section through a can according to the invention and

FIG. 4 shows a section through a part of the sealing membrane, and

FIGS. 5 a-5 c show schematic sections through variants of the sealing membrane.

The can 1 shown in FIG. 3 comprises a can body 2 which has a jacket 4 which, for example, is cylindrical or rectangular. The can body 2 has a base 3 and, opposite the latter, a retaining ring 6 which is fitted tightly to the jacket 4. The jacket 4 can intrinsically be produced from any desired suitable material, for example from tinplate, steel, plastic or coated paper. The retaining ring 6 can be uncoated, coated or varnished. It can be produced, for example, from tinplate, steel or aluminum.

According to FIG. 1, the retaining ring 6 has an inwardly oriented flange 7, which projects substantially vertically from an upper rim 5 of the jacket 4. A sealing membrane 8 is peelably fixed to this flange 7. The peelable fixing of such a sealing membrane 8 is known to those skilled in the art and therefore does not need to be explained further here.

The sealing membrane 8 is produced from a composite film which, for example according to FIG. 4, has a print A and layers B and C. The total density of the sealing membrane 8 is, for example, 0.05 mm and in particular 0.03-0.15 mm. The uppermost layer A forms the print, with which an upper side 11 of the sealing membrane 8 is printed and, for instance, can constitute a photograph and statements about the content of the can 1. The print can be a gravure print, a digital print or a flexo print. The layers B and C can be thin sheets produced from plastic, for example polyester, paper or aluminum. Still further layers are also conceivable, for example a layer of PP-peel.

During the printing of the sealing membrane 8, an adhesive 10 is applied to the layer B at the same time. FIG. 4 shows the adhesive 10, which is in the region of the layer A. The adhesive 10 is applied to the layer A, for example by way of a gravure printing roll. This preferably takes place at the same time as the application of the print A. The adhesive 10 is preferably a sealing wax, which can have one or more components. An adhesive 10 or sealing wax which is sterilizable is preferably used. Also conceivable, however, is a non-sterilizable adhesive 10. The sterilization temperature is, for example, 128° Celsius. The adhesive 10 is produced, for example, on the basis of a polyester resin, polyester copolymer, polyurethane or PVC.

The adhesive 10 is used for the detachable fixing of the pull tab 9, folded over or folded according to FIG. 1. In the closed state of the can 2, the pull tab 9 is therefore fixed in the folded-over or folded position shown in FIG. 1. This is also the case when the sealing membrane 8 is produced from a composite film which has a high restoring force. Without this adhesive 10, the pull tab 9 would protrude from the upper side 11. The adhesive 10 is arranged between the pull tab 9 and the upper side 11 in a region 11 a. The adhesive 10 can be applied to the upper side 11 and/or to the upper side of the pull tab 9. After the printing of the sealing membrane 8 and the sealing of the sealing membrane 8 onto the retaining ring 6, the pull tab 9 is bent over into the position shown in FIG. 1. The pull tab 9 is fixed in the position shown by welding. As a result of the welding, detachable adhesion between the printed adhesive regions or an adhesive region and a surface is produced. This can be done in a manner known per se, for example by using a permanently heated bar or ultrasound. The sealing membrane 8 is preferably connected to the retaining ring 6 before the connection of the pull tab 9.

In the embodiment shown in FIG. 5 a, the adhesive 10 is printed onto the upper side of the uppermost layer B separately from a further print A′. Here, the layer B is, for example, a film made of polyester. In principle, the further print A′ could also be left out.

In the embodiment according to FIG. 5 b, the adhesive 10 is printed onto a further print A″. During the production of the sealing membrane in accordance with FIG. 5 b, the print A″ is thus printed onto the layer B first and the adhesive 10 is then printed onto the layer A″.

In the embodiment according to FIG. 5 a, a further print A″ is printed onto the underside of the layer B or onto the upper side of the layer C, while the adhesive is printed onto the upper side of the layer B.

In order to open the can 2, the pull tab 9 according to FIG. 1 is gripped by hand and pivoted upward in the direction of the arrow 14. If a pull is then exerted on the pull tab 9 in the direction of the arrow 13 in accordance with FIG. 3, the sealing membrane 8 can be pulled completely off the retaining ring 6. The can 2 then has an opening 15, through which the content of the can 2 can be removed. Of course, the sealing membrane 8 can also be pulled off only partly. Re-closure of the can 2 is possible, for example, by using a lid, not shown here, which can be placed on the retaining ring 6.

LIST OF DESIGNATIONS

-   1 Can -   2 Can body -   3 Base -   4 Jacket -   5 Rim -   6 Retaining ring -   7 Flange -   8 Sealing membrane -   9 Tab -   10 Adhesive -   11 Upper side -   12 Underside -   13 Arrow -   14 Arrow -   15 Opening -   A Print -   B Layer (thin sheet) -   C Layer (thin sheet) 

1-15. (canceled)
 16. A method for producing a can comprising a jacket-shaped can body which has at least one opening that is tightly closed by a peelable sealing membrane and which is provided with a pull tab which is folded over and detachably connected to an upper side of the sealing membrane, wherein an adhesive is applied to the upper side of the sealing membrane and/or to the pull tab by means of a printing process, and in that the pull tab is detachably connected to the upper side of the sealing membrane by this adhesive.
 17. The method as claimed in claim 16, wherein the adhesive is a varnish and in particular a sealing wax.
 18. The method as claimed in claim 16, wherein the adhesive is printed on by gravure printing, flexo printing, digital printing, screen printing or offset printing.
 19. The method as claimed in claim 16, wherein the pull tab, after being folded over, is connected to the upper side of the sealing membrane by welding.
 20. The method as claimed in claim 16, wherein the can is sterilized with the sealing membrane fitted.
 21. The method as claimed in claim 16, wherein the sealing membrane is produced from a composite film having a plurality of layers.
 22. The method as claimed in claim 21, wherein the composite film has at least one layer of plastic.
 23. A can produced by the method as claimed in claim 16, wherein the adhesive is printed on.
 24. The can as claimed in claim 23, wherein the sealing membrane is produced from a composite film.
 25. The can as claimed in claim 23, wherein the sealing membrane is peelably connected to a retaining ring.
 26. The can as claimed in claim 23, wherein the sealing membrane has a high restoring force.
 27. The can as claimed in claim 23, wherein the adhesive withstands sterilization.
 28. The can as claimed in claim 23, wherein the sealing membrane comprises an upper layer, and in that the adhesive is arranged on the upper side of this upper layer separately from a further print.
 29. The can as claimed in claim 28, wherein the further print is arranged on the underside of the upper layer.
 30. The can as claimed in claim 23, wherein the adhesive is printed onto the upper side of a print. 